UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: June 18, 2015 

SUBJECT: Diquat Di bromide: Tier I Review of Human Incidents for Draft Risk Assessment 

PC Code: 032201 DP Barcode: 0427720 

Decision No.: 482019 

Petition No.: A 

Risk Assessment Type: A 

TXR No.: A 

MRIO No.: NA 

Registration No.: NA 

Regulatory Action: A 

Case No.: A 

CAS No.: 85-00-7 

40 CFR: NA 

Vcr.Apr.08 

FROM: Elizabeth Evans, Environmental Protection Specialist 

Toxicology and Epidemiology Branch c;_ ~';hA/J/ c;\At~ 

~~~ 

Health Effects Division (7509P) 

and 

Shanna Recore, Industrial Hygienist 

Toxicology and Epidemiology Branch 

THROUGH: 

TO: 

Health Effects Division (7509P) /,) 

David J. Miller, Acting Branch Chief J _A;. J ~If.. Toxicology and Epidemiology Branch 

Health Effects Division (7509P) 

Thurston Morton, Risk Assessor 

Risk Assessment Branch I 

Health Effects Division (7509P) 

and 

Bonnie Adler, Chemical Review Manager 

Risk Management & Implementation Branch 3 

Pesticide Re-evaluation Division (7508P) 

Summary and Conclusions 

Diquat dibromide incidents were previously reviewed on June 11 , 2009. This incident review 

found that " ... the evaluation of incident data for diquat dibromidejinds a relatively loiv volume 

of incidents ... only 57 incidents, symptoms appear generic and not confirmed to be related to 

exposure. there is no clear evidence of a trend or exposure pallern. Therefore. at this time, there 

are no remarkable case reports which suggest a plausible association between a moderate or 

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severe health outcome and exposure 10 pesticide diquat dibromide nor can we discern any 

suggestion of a trend or pattern regarding the health effects due to the alleged exposure to 

pesticide diquat dibromide. The current review of the incident data does not warrant further 

investigations at this time. "(Hawkins, 2009) 

The current IDS analysis, from January I, 20 I 0 to May 28, 20 15, found 18 incidents repor1ed to 

Main IDS involving the single active ingredient, diquat di bromide. Fourteen of these incidents 

were classified as moderate severity and four incidents were classified as major severity. There 

are 85 additional incident reported to Main IDS that involve multiple active ingredients, 

including diquat di bromide. In Aggregate IDS, from January I, 20 I 0 to May 28. 2015, there are 

1121 incidents reported involving diquat dibromide. 

The query of SENSOR-Pesticides 1998-2011 identifies 11 9 cases involving diquat di bromide, 32 

of which involve a single active ingredient. 

Detailed Review 

I. ACTION REQUESTED 

Oiquat dibromide is being considered under the FQPA-mandated Registration Review program 

established to review, on a 15 year cycle. pesticides for which a Re-registration Eligibility 

Decision has been made. One component of the Agency's Registration Review Program is 

consideration of human incident data. In conjunction with a human health risk assessment based 

on other data sources, such human incident data can assist the Agency in better defining and 

characteri zing the risk of pesticides/pesticide products. 

Reports of adverse health effects allegedly due to a specific pesticide exposure (i.e. , an 

" incident'") are large ly self-reported and therefore, generally speaking, neither exposure to a 

pesticide or reported symptom (or the connection between the two) is validated or otherwise 

confirmed. Typically, causation cannot be determined based on incident data. However, 

incident information can be an important source of feedback to the Agency: incidents of severe 

outcome. or a suggested pattern or trend among less severe incidents, can signal the Agency to 

further investigate a particular chemical or product. Observational epidemiology studies relate 

the risk of disease, e.g., cancer, and exposure to an agent such as a pestic ide product in the 

general population or specific sub-groups like pesticide applicators. 

II. BACKGROUND 

Oiquat dibromide is a non-selective contact herbicide, algicide, desiccant, and defoliant. As an 

herbicide/a lgicide, it is used to control broad leaf and grassy weeds in non-crop (including 

residential) and aquatic areas. As a desiccant/ defoliant, it is used in seed crops and potatoes. Its 

largest use is as a desiccant on potato crops. Diquat dibromide is formulated as a soluble 

concentrate and ready-to use liquid. As an herbicide, it is applied using a hand-held or 

mechanical sprayer; as an algicide, it is injected below the water surface to control submerged 

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weeds. When used as a desiccant, it may be applied by aircraft or ground equipment. 

Applications in crop areas are made five days to two weeks before harvest. 

For this evaluation, both OPP Incident Data System (IDS) and the Centers for Disease Control 

and Prevention/National Institute for Occupational Safety and Health (CDC/NIOSH) Sentinel 

Event Notification System for Occupational Risk-Pesticides (SENSOR) databases were 

consulted for pesticide incident data on the active ingredient diquat dibromide (PC Code: 

03220 I). The purpose of the database search is to identify potential patterns in the frequency 

and severity of the health effects attributed to diquat dibromide exposure. 

III. RES UL TS!DISCUSSION 

a. IDS (Incident Data System) 

opp· s IDS includes reports of alleged human health incidents from various sources, including 

mandatory Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) Section 6(a)(2) reports 

from registrants, other federal and state health and environmental agencies. and individual 

consumers. Since 1992. OPP has compiled these reports in IDS. IDS contains reports from 

across the U.S. and most incidents have all relevant product information recorded. Reports 

submitted to the IDS represent anecdotal reports or allegations only, unless otherwise stated in 

the report. 

IDS records incidents in one of two modules: Main IDS and Aggregate IDS: 

o Main IDS contains incidents resulting in higher severity outcomes and provides 

more detail with regard to case specific. This system stores incident data for 

death, major and moderate incidents, and it includes information about the 

location, date and nature of the incident. Main IDS incidents involving only one 

pesticide are considered to provide more certain information about the potential 

effects of exposure from the pesticide. 

o Aggregate IDS contains incidents resulting in less severe human incidents (minor, 

unknown, or no effects outcomes). These are reported by registrants only as 

counts in what are aggregate summaries. 

From January 1, 2010 to May 28. 2015, there were 18 incidents reported to Main IDS involving 

the single active ingredient, diquat di bromide. Fourteen of these incidents were classified as 

moderate severity and four incidents were classified as major severity. Two of the major 

severity incidents were the result of unintentional ingestion of the product that had been repacked 

in a beverage container. The details of the incidents classified as major severity are found in 

Table l. There are 85 additional incident reported to Main IDS that involve multiple active 

ingredients, including diquat dibromide. 

From January I, 2010 to May 28, 2015, there are 1 12 1 incidents reported to Aggregate IDS 

involving diquat di bromide. Three of these incidents had no or unknown effects and 11 18 of 

these incidents were classified as minor severity. For minor severity incidents, the effects 

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experienced were generally minimally traumatic and resolving rapidly and usually involve skin. 

eye or respiratory irritation. 

Incident 

Package 

Re t Incident Reg 

Date Location Number Product Name Incident Description 

A 56 year old male applied the 

product to a body of water on a windy 

day and he inhaled some of the 

product. He experienced 

hypothermia, persisting pulmonary 

02 1807 - REWARD infiltrates with associated shortness of 

00007 SHREVEPORT, (NON- breath and low 02 saturation, 

3/ 15/20 I 0 LA NA SPECIFIC) respiratory fai lure and sweating. 

A 2 year old boy suffered a severe 

asthma anack and had to be 

REG LO E hospitalize following application of 

023289 - (NON- this product to neighboring potato 

00004 8/30/2011 NE NA SPECIFIC) fi eld. 

An adult male put some product in a 

soda bottle with the intention of 

REWARD applying it to a field. He accidentally 

LANDSCAPE drank about one ounce of the product. 

AND He experienced vomiting, throat 

024186 - 000 100- AQUATIC irritation, burns to his throat and lips. 

00200 5/ 16/20 12 MS 0109 1 HERBICIDE increased creatinine. 

A 3 year old boy accidentally 

ingested product that was stored in a 

Gatorade bo11le. He experienced 

REWARD burned lips, blistered tongue and renal 

02522 1 - AQUATIC damage. He was hospitalized for I 0 

00005 2/4/20 11 CA NA HERBICIDE days. 

The most implicated product is RoundUp Weed & Grass Killer Concentrate Plus (Reg. No. 

71995-29). It is impli cated in 50% of the diquat dibromide incidents reported to IDS. This 

product contain 0.73% diquat dibromide and 18% glyphosate. It is used around flowerbeds, 

landscapes, trees, driveway, walkways, and along fences to control weeds. 

b. SENSOR-Pesticides 

The SENSOR-Pesticides database covers 12 states from 1998-2011 , although reporting varies 

from state to state. Cases of pesticide-related illnesses arc ascertained from a variety of sources, 

including: reports from local Poison Control Centers, state Department of Labor workers' 

compensation claims when reported by physicians, reports from State Departments of 

Agriculture, and physician reports to state Departments of Health. Although both occupational 

and non-occupational incidents are included in the database, SENSOR focuses on occupational 

pesticide incidents, and is of particular value in providing that information. A state SENSOR 

contact specialist attempts to follow-up with cases and obtains medical records to verify 

symptoms, circumstances surTounding the exposure, severity, and outcome. Using standardized 

protocol and case definitions derived from poison center reporting, SENSOR coordinators at 

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State Departments of Health enter the incident interview description provided by the case. 

medical report, physician and patient into the SENSOR data system. The SENSOR data system 

is accessible to participating states and EPA. 

SENSOR-Pesticides identified a total of 116 cases involving diquat dibromide (pc code 032201 ). 

Of these. 32 cases involve a single active ingredient which will be analyzed in this memo. 

Sixteen cases were work-related and 16 cases were not work-related. Examples of diquat 

application targets that resulted in cases made ill include landscaping (n=5), aquatic (n=6), and 

weed control (n=4). While half of the cases were applying the product at the time they were 

exposed, 13 bystander cases were reported as well (the remaining four cases had no reported 

application target). Products most implicated among cases were: 10 cases involved Reward 

Landscape and Aquatic Herbic ide (mainly under reg. # I 00-109 l ); 7 cases involved Moss-Out 

(Reg # I 1694-40) 

Two cases were high in severity, four cases were moderate in severity and 26 cases were low in 

severity. The most commonl y reported health effects were dennal (n= l 9) mainly rash and 

irritation, followed by ocular (n= 11) including eye irritation. It is notable, however, that of the 

four moderate severity cases. symptoms included: corneal abrasion. burning of skin, and 

blistering skin. Both high severity cases reported renal health effects and one also reported 

cardiovascular symptoms. ln one high severity case the cases made an aquatic application to a 

lake on his property and proceeded to rake the shore for several hours. The case developed a 

headache and troubl e breathing and was admitted to the ER with respiratory, gastrointestinal, 

neurological, renal and cardiovascular symptoms. The second high severity case was 

occupational; a vegetation management supervisor was in a chemical storage room taking 

inventory. Some 2.5 gallon containers were improperly stored on the top shelf and the employee 

decided to relocate them. When he reached up to move a container, the lid was not on it and the 

material spilled into his face. The person swallowed some of the herbi cidal desiccant. He 

immediately took a full body shower and was taken for medical care. The next day he was 

hospitalized due to progressive respiratory and gastrointestinal symptoms and discharged after 

10 days. 

c. Agricultural Health Study (AHS) 

The AHS is a high quality, prospective epidemiology study evaluating the link between pestic ide 

use and various health outcomes including cancer. The AHS includes private and commercial 

pesticide applicators and their spouses. If there are AHS findings relevant to a particular 

pesticide going through registration review. the Agency will ensure they are considered in the 

problem formulation/scoping phase of the process and, if appropriate, fully reviewed in the risk 

assessment phase of the process. The AHS includes information on use of 50 different pesticide 

active ingredients commonly used in agriculture. Diquat dibromide is not included in the AHS 

and therefore this study does not provide information for this report. 

CONCLUSION 

Aggregate IDS identities a moderate frequency of minor severity cases (n=l 121) involving 

diquat dibromide: whereas IDS Main identifies only 18 cases (moderate and high severity) 

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involving diquat dibromide. Diquat is registered for homeowner uses and available at garden 

centers and is often mixed with other chemicals such as glyphosate. With regard to moderate 

and high severity diquat case reports, there is a low frequency of cases in both IDS (n= l 8) and 

SENSOR-Pesticides (n=6). However, the symptoms of these high and moderate cases are 

generally serious. Further, it is notable that two of the four high severity incidents report in I OS 

involve the accidental ingestion of diquat from a repurposed beverage container. The Agency 

will continue to monitor the diquat incidents. 

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